Thirty-two children with extramedullary myeloid cell tumour (EMT) who const
ituted 41 per cent of children with acute myeloid leukaemia (AML) were stud
ied to ascertain their laboratory characteristics and potential problems in
diagnosis. The diagnosis, established by peripheral blood smear and/or bon
e marrow examination, was AML (n = 29) and refractory anaemia with excess b
lasts in transformation (RAEB-t; n = 3), The six referred patients in whom
the diagnosis had been missed, and two cases wrongly reported as histiocyto
sis on aspiration cytology, were those in whom a peripheral blood smear had
not been examined, It is concluded that diagnostic work-up of proptosis mu
st include a full haemogram, meticulous peripheral blood smear examination,
repeated if necessary, and bone marrow examination where relevant. RAEB-t
cases with extramedullary myeloid cell tumour should be classified as acute
myeloid leukaemia.